Agenesis of the Right Internal Carotid Artery Associated with Persistence of the Primitive Olfactory Artery. A Case Report.

Abstract

Unilateral agenesis of the internal carotid Artery (ICA) is an extremely rare developmental anomaly. The absence of an ICA was first described by Tode in 1787 after being discovered during a postmortem examination. Only approximately 100 cases have been reported in the literature with a left predominance (3:1). When a unilateral ICA is absent, collateral circulation is sufficient to maintain cerebral function with few or no neurologic symptoms. Most patients with ICA agenesis present with focal neurologic signs, such as convulsions, headache, or transient ischemic attack, and ICA agenesis may be associated with aneurysm, hemorrhage, cerebral Hypoplasia, hemangioma, or anomalous vascular anastomosis. During dissection carried out in the Anatomy laboratory an absence of the right internal carotid artery was found. The specimen consists of a brain from a male cadaver with absence of the right internal carotid artery. A common trunk arises from the anterior aspect of the left internal carotid artery to supply the territory corresponding to the right internal carotid artery. Just anterior to the right middle cerebral artery this common trunk gives rise to two small vessels and then splits into two terminal branches. These two small vessels probably correspond to a persistent primitive olfactory artery (PPOA, embryological vessel). Six different branching patterns of circulation in cases of absence of internal carotid artery have been described for many authors; this paper describes a branching pattern of circulation previously undescribed.